This invention is an improvement on this inventor's prior U.S. Pat. No. 7,086,435 B1. Also, other teachings of tree harvesting, cutting and gripping apparatus mounted on the end of an adjustable boom are illustrated in U.S. Pat. Nos. 6,408,906 B1; 3,532,141; 3,536,113; 4,269,241 and 6,123,124.
For some years, tree severing mechanisms or felling heads have been mounted on the end of extendable booms which are operable from a motorized vehicle, something similar to a “cherry picker”. These vehicles are maneuverable and can negotiate in very limited space. These manipulated felling heads cause much less damage to the surrounding environment or structures. The felled tree bolts are not allowed to drop to the ground or be dragged along the forest floor, crushing and uprooting young saplings, much less being allowed to flatten someone's dwelling.
The first tree harvesters merely severed the tree at its base and allowed it to fall without thought as to direction or damage. Then, loggers began to ascend trees delimbing as they went. Direction to tree fall was supplied by tying a rope or line to the top of the tree and pulling the same by hand or tractor in a preferred direction while being severed at the tree base. The third harvesting practice was the use of a crane supporting a platform for a tree climber wielding a chain saw to trim limbs and cut short tree bolts.
Most of today's tree harvesting of this type occurs in congested area, such as housing developments, where movement in confined areas is critical. Thus, the cut tree top or other cut tree bolts cannot be released and allowed to free fall to the ground and risk damaging structures, power lines and prized fruit trees. Therefore, the cut portion must be lowered to the ground while still in the grasp of the machine. Since trees vary in size and weight, risks are taken on some occasion when the actual weight of the cut portion of the tree is so heavy as to overload the boom and cause the entire mechanized unit to tip over.
The monitoring and measuring the weight of a fixed load on a boom end or forklift has been taught by U.S. Pat. Nos. 3,990,584; 3,993,166; 4,456,093 and 4,746,024 which are hereby incorporated by reference. In U.S. Pat. No. 7,086,435 B1, the inventor (who is the same as the subject inventor) taught a weighing means for a severed tree bolt which was an improvement over the art at that time but not accurate enough for some critical applications. The objection is that calculating the weight of an object on the end of an extended boom is affected by the rigidity of the extended boom, wind pressure acting on the boom and cut tree bolt section and the stability of the base machine platform from which it extends. Any bobbing up and down by the weighted object will cause fluctuations in the measurements which may already exceed the limits of reliability for safety purposes. Also, an over-the-limit weighing tree top or bolt once removed from the free standing tree could topple over the support vehicle and releasing the tree top once the toppling movement had begun would be too late to rectify the situation.
Of particular concern in the cutting of free standing trees or large limbs extending therefrom is the binding of the saw blade while passing through the tree forming the kerf, the kerf being the incision made in the tree by the saw blade. As the kerf is being formed, the tree due to gravity or a spring load within the tree itself will tend to close the kerf thus impinging upon the saw blade and preventing any further saw blade movement. Upon such an occurrence, moving parts such as the saw blade chain may shear and separate with considerable force. Thus, not only will the saw blade chain disintegrate sending out shrapnel in all directions endangering those around but also will completely interrupt and bring to a standstill all cutting operations. Those familiar with any woodworking operation is appreciative of the consequences resulting from the binding of a cutting saw blade while still in the kerf.
The motorized vehicle with the extendable boom is made by Manitou North America, Inc. of Waco, Tex., and is well known in the trade. The Manitou Model MRT 2150 and other similar devices incorporate a computerized system for measuring and displaying the weight of a load of construction material placed on a forklift mounted on the end of a boom. The turntable on which the boom of the Manitou apparatus is situated can rotate 360 degrees. The end of the boom upon which the subject tree severing mechanism is mounted can be lowered to essentially ground level or be raised to a height of at least 80 feet. The Manitou apparatus also has means for measuring and displaying the height at which the end of the boom is located and imputing that height as a signal to a computer. Further, this apparatus has means for measuring and displaying the horizontal distance between the center of the boom turntable and the projected location of the tree severing apparatus measured on the horizontal plane passing through the base of the boom. A signal representing this distance is also imputed to the Manitou apparatus computer as one factor in helping determine the likelihood of the Manitou apparatus tipping over when the boom end is at a particular height, angle and is carrying a particular load.
In the prior art, many different types of mechanisms have been used to create the side to side tilting motion of the felling head. Some systems use a pair of hydraulic actuators mounted on the felling head to achieve the tilting motion. However, these prior art arrangements tend to be bulky, heavy and expose certain moving part to the rigorous environment of the logging industry.
Thus, a principal object of this invention is to provide a tree harvesting apparatus and method for general use but particularly adapted for use in a crowded suburban or business area. This apparatus enables a tree top or cut log bolt being harvested to be gripped and weighed prior to being lowered or allowed to free fall to the ground.
Another primary object of this invention is to provide means for grasping a standing tree in a manner that will allow the cutting means, i.e., chain saw or rotation blade, to form a kerf in the tree that will not bind the cutting means.
Another object of this invention is to provide a tree cutting head mounted on an extending boom that is rotatable in both a plane being horizontal to the ground or base area and in a plane being perpendicular to the ground through a 180 degree arc in each plane.
Other objects and features of this invention will become apparent by reference to the following drawings and description.